fix(text): clean echoed ID tags out of rendered replies

index.ts

@@ -69,7 +69,7 @@ const server: Plugin = (async (ctx) => {
             prompts,
             hostPermissions,
         ) as any,
-        "experimental.text.complete": createTextCompleteHandler(),
+        "experimental.text.complete": createTextCompleteHandler(state),
         "command.execute.before": createCommandExecuteHandler(
             ctx.client,
             state,

lib/hooks.ts

@@ -289,12 +289,15 @@ export function createCommandExecuteHandler(
     }
 }
 
-export function createTextCompleteHandler() {
+export function createTextCompleteHandler(state: SessionState) {
     return async (
         _input: { sessionID: string; messageID: string; partID: string },
         output: { text: string },
     ) => {
-        output.text = stripHallucinationsFromString(output.text)
+        // The session format decides which tags are recognised: compact sessions
+        // emit @7@ refs, and cleaning with the default XML rules leaves them in
+        // the rendered reply (#632).
+        output.text = stripHallucinationsFromString(output.text, state.idFormat)
     }
 }
 

lib/messages/utils.ts

@@ -11,6 +11,15 @@ const DCP_UNPAIRED_TAG_REGEX = /<\/?dcp[^>]*>/gi
 const INJECTED_MESSAGE_ID_SUFFIX_REGEX = /(?<=\n)<dcp-message-id[^>]*>m\d+<\/dcp-message-id>\s*$/
 const HALLUCINATED_PARAMETER_SUFFIX_REGEX = /(?<=\n)m\d+<\/parameter>\s*$/
 const COMPACT_TAG_REGEX = /@(?:[1-9]\d*|b[1-9]\d*|blocked)@(?:[ \t]+\[(?:low|medium|high)\])?/gi
+// Models that imitate the injected tag often emit broken fragments instead of a
+// well formed one: a run of trailing lines made only of bracket debris such as
+// "<<", "<" or "<m0477" (see #562). The run is anchored to the end of the reply
+// and needs at least two lines, so a lone "<" in prose, markdown or code stays
+// intact.
+const DEGENERATE_TAG_LINE_PATTERN = String.raw`[ \t]*<{1,2}\/?[ \t]*(?:dcp[a-z-]*|m\d+|b\d+)?[ \t]*>?[ \t]*`
+const DEGENERATE_TAG_DEBRIS_REGEX = new RegExp(
+    String.raw`(?:\n${DEGENERATE_TAG_LINE_PATTERN}){2,}\n?$`,
+)
 
 const generateStableId = (prefix: string, seed: string): string => {
     const hash = createHash("sha256").update(seed).digest("hex").slice(0, SUMMARY_ID_HASH_LENGTH)
@@ -175,6 +184,7 @@ export const stripHallucinationsFromString = (text: string, format: IdFormat = "
     return withoutKnownSuffixes
         .replace(DCP_PAIRED_TAG_REGEX, "")
         .replace(DCP_UNPAIRED_TAG_REGEX, "")
+        .replace(DEGENERATE_TAG_DEBRIS_REGEX, "")
 }
 
 export const stripHallucinations = (messages: WithParts[], format: IdFormat = "xml"): void => {

tests/hooks-permission.test.ts

@@ -269,7 +269,7 @@ test("command execute exits after effective permission resolves to deny", async
 
 test("text complete strips hallucinated metadata tags", async () => {
     const output = { text: "alpha <dcp>beta</dcp> omega" }
-    const handler = createTextCompleteHandler()
+    const handler = createTextCompleteHandler(createSessionState())
 
     await handler({ sessionID: "session-1", messageID: "message-1", partID: "part-1" }, output)
 

tests/message-priority.test.ts

@@ -765,7 +765,7 @@ test("hallucination stripping removes all dcp-prefixed XML tags including varian
 
     assert.equal(stripHallucinationsFromString(text), "alphaomega")
 
-    const handler = createTextCompleteHandler()
+    const handler = createTextCompleteHandler(createSessionState())
     const output = { text }
     await handler({ sessionID: "session", messageID: "message", partID: "part" }, output)
     assert.equal(output.text, "alphaomega")

tests/text-cleanup.test.ts

@@ -0,0 +1,87 @@
+import assert from "node:assert/strict"
+import test from "node:test"
+import { mkdtempSync, rmSync } from "node:fs"
+import { join } from "node:path"
+import { tmpdir } from "node:os"
+
+const root = mkdtempSync(join(tmpdir(), "dcp-text-cleanup-"))
+process.env.XDG_DATA_HOME = join(root, "data")
+process.env.XDG_CONFIG_HOME = join(root, "config")
+process.env.OPENCODE_CONFIG_DIR = join(root, "config", "opencode")
+test.after(() => rmSync(root, { recursive: true, force: true }))
+
+const { createSessionState } = await import("../lib/state")
+const { stripHallucinationsFromString } = await import("../lib/messages/utils")
+const { createTextCompleteHandler } = await import("../lib/hooks")
+
+// Verbatim from #562: the reply a model produced after being shown the
+// <dcp-message-id> tag, with every fragment of that tag left unclosed.
+const KIMI_REPLY = [
+    "Which do you prefer?",
+    "<<",
+    "<<",
+    "<<",
+    "<<",
+    "<<",
+    "<<",
+    "<<",
+    "<",
+    "<m0477",
+    "<",
+    "<",
+    "<",
+].join("\n")
+
+test("broken tag debris at the end of a reply is removed", () => {
+    assert.equal(stripHallucinationsFromString(KIMI_REPLY), "Which do you prefer?")
+})
+
+test("a single stray angle bracket is left alone", () => {
+    const code = "if (a<b && c>d) {\n  return 1\n}"
+    assert.equal(stripHallucinationsFromString(code), code)
+
+    const prose = "Compare a < b"
+    assert.equal(stripHallucinationsFromString(prose), prose)
+
+    const oneLine = "The tag looks like <m0477"
+    assert.equal(stripHallucinationsFromString(oneLine), oneLine)
+})
+
+test("debris that is not at the end of the reply is left alone", () => {
+    // Cleanup is deliberately conservative: only a trailing run is removed, so
+    // bracket-only lines in the middle of a reply are never rewritten.
+    const text = ["intro", "<<", "<m0477", "still talking"].join("\n")
+    assert.equal(stripHallucinationsFromString(text), text)
+})
+
+test("code blocks containing brackets are not touched", () => {
+    const text = ["```ts", "<<", "<", "```", "done"].join("\n")
+    assert.equal(stripHallucinationsFromString(text), text)
+})
+
+test("well formed injected tags are still stripped", () => {
+    assert.equal(
+        stripHallucinationsFromString("answer\n<dcp-message-id>m0477</dcp-message-id>"),
+        "answer\n",
+    )
+    assert.equal(stripHallucinationsFromString("m0477</parameter>"), "m0477</parameter>")
+})
+
+test("text.complete strips echoed refs for compact sessions", async () => {
+    const state = createSessionState("compact")
+    const handler = createTextCompleteHandler(state)
+
+    // Verbatim from #632: a model copying the compact reference tag into its
+    // reply. The handler used the XML cleanup rules, which do not match @N@.
+    const output = { text: "I will use @7@ [high] to compress.\n@b1@ done\n@blocked@" }
+    await handler({ sessionID: "ses", messageID: "m", partID: "p" }, output)
+    assert.equal(output.text, "I will use  to compress.\n done\n")
+})
+
+test("text.complete leaves ordinary compact text untouched", async () => {
+    const state = createSessionState("compact")
+    const handler = createTextCompleteHandler(state)
+    const output = { text: "mail me at [email protected], see <https://x.dev> for the patch" }
+    await handler({ sessionID: "ses", messageID: "m", partID: "p" }, output)
+    assert.equal(output.text, "mail me at [email protected], see <https://x.dev> for the patch")
+})